Implant Placement Depth and Peri-Implant Tissue Outcomes

The primary aim of this randomized clinical trial is to evaluate the influence of subcrestal implant placement depth (-2 mm vs -4 mm) on peri-implant marginal bone level changes, including marginal bone loss and bone remodeling. Secondary outcomes include implant success, peri-implant probing depth (PPD), and bleeding on probing (BoP). Partially edentulous patients requiring fixed implant-supported prosthetic rehabilitation with two implants in posterior maxillary or mandibular regions will be included. Implants will be placed subcrestally at either -2 mm or -4 mm from the bone crest, following a submerged healing protocol. Allocation to insertion depth will be randomized. Marginal bone level changes will be assessed using standardized periapical radiographs at second-stage surgery, prosthesis placement, and at 1, 3, 6, and 12 months after functional loading. PPD and BoP will be recorded at the same time points.

Inclusion Criteria: * Patients ≥18 years old with partial edentulism. * Need for rehabilitation with fixed implant-supported prostheses in posterior regions. * Availability of minimum bone height for implants ≥6 mm in length. * Minimum bone width without the need for guided bone regeneration. * Supracrestal soft tissue thickness ≥2 mm. * Non-smokers or smokers of ≤10 cigarettes/day. * Plaque index and bleeding on probing \<20%. * Probing depth ≤3 mm. * Signed informed consent. Exclusion Criteria: * Systemic diseases contraindicating implant surgery. * Treatment with intravenous bisphosphonates. * Head and neck radiotherapy. * Uncontrolled diabetes. * Pregnancy or breastfeeding. * Alcohol or drug use. * Psychiatric disorders. * Need for bone regeneration procedures. * Inability to complete follow-up. * Implant failure during the study period.